High aspect ratio 3D semiconductor nanostructures, such as silicon nanowires, may have a profound effect on the design and performance of many types of devices, including batteries, solar cells, detectors and thermoelectric systems. To produce silicon nanowires, either a bottom-up growth method based on a metal catalyzed vapor liquid solid (VLS) mechanism or a top-down method based on lithography and etching are typically used. The VLS method generates nanowires with smooth sidewalls, and nanowire diameter and orientation may in principle be controlled by epitaxial growth on appropriate substrates. However, uniformity and scalability remain as challenges for the bottom-up growth paradigm.
Si light emission was first discovered by Canham in 1990 and emission in the entire visible as well as ultraviolet (UV) light range is of interest for various applications. Traditionally, blue and UV light emission from silicon has been obtained through the sonication of porous silicon and immersion in H2O2 for several hours to generate small discrete nanoparticles. It is desirable to have a method that can produce tunable light emission/absorption over a broad range of the electromagnetic spectrum—from IR to UV—in a manufacturable fashion.